化简：2sin(π/4+θ)sin(π/4-θ)=?

化简sin(α+β)+sin(α-β)+2sinαsin(3π/2-β)= 化简：2sin(π/4+θ)sin(π/4-θ)=? 化简 {sin(π+α)cos(α-2π)tan9π/4}/sin(-α)sin(7π/2+α)过程 化简sin(π/4+a)+sin(π/4-a) 化简sin(4π-a)*sin(5π-a)=? 化简:sin(-a)cos(2π+a)sin(-a-π) 求值：（tan10°-√3）×cos10°/sin50° 求证：[sin（2α+β）]/sinα- 2cos（α+β）=sinβ/cosα 化简cosθ+cos（θ+2π/3）+cos（θ+4π/3） 证明：sin（α+β）sin（α-β）=sin^2α-sin^2β 2sin(x+π/4)sin(x-π/4)=? 1-2sin²π/8=sinπ/4 根号2sin(x+π/4)化简 化简sin(2π+a) sin^2(π/4 +x) 化简求值sin^4θ+sin^4(π/3-θ)+sin^4(π/3+θ) sin^4θ+sin^4(π/3-θ)+sin^4(π/3+θ)化简求值 化简sin(A+π/4)sin(A-π/4)/sin^4A-cos^4A 化简sin(π/4+α)cosα-sin(π/4-α)sinα 化简sin^2(α-π/6)+sin^2(α+π/6)-sin^2α 化简；sin^2 A+sin^2(A-π/3)+sin^2(A+π/3)